JPH0833313A - Snubber circuit for power converter - Google Patents

Abstract

PURPOSE:To obtain a snubber circuit for power converter employing a semiconductor switching element in which a power supply or a load can be regenerated. CONSTITUTION:A switching circuit 2 and a load 3 are connected in parallel with a DC power supply 1 and a snubber circuit 10, comprising a first capacitor 14, a first diode 12, and a second capacitor 15 forming a CDC series circuit, is connected in parallel with the switching circuit 2. A series circuit of a first reactor 16 and a second diode 11, is connected between the anode of the first diode and the negative power supply side while a series circuit of a second reactor 17 and a third diode 13 is connected between the cathode of the first diode and the positive power supply side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber circuit for reducing an overvoltage and a switching loss applied to a semiconductor switch element when the semiconductor switch element is turned off in a power converter using the semiconductor switch element.

[0002]

2. Description of the Related Art It is well known that power conversion can be performed by configuring a power conversion device with a semiconductor switch element and turning on / off the semiconductor switch element. The switching operation (turn-on or turn-off) of the semiconductor switch element is known. ), The current waveform and the voltage waveform have an overlapping period (the overlapping period is a period during which current flows while voltage is applied), resulting in a transient power loss (so-called switching loss).
Occurs, and the voltage rise rate (dv / d
There is a possibility that the semiconductor switch element will be destroyed due to t).

Therefore, a snubber circuit composed of a reactor, a capacitor and the like has conventionally been inserted in a power conversion device to suppress the rate of voltage rise, shorten the overlapping period as much as possible, and reduce the generated loss. The energy absorbed by the snubber circuit is regenerated to a power source or a load to suppress a decrease in efficiency of the power conversion device. FIG. 6 is a circuit configuration diagram of a first conventional example of a power conversion device.

In FIG. 6, 1 is a direct current source, 2 is a switching circuit in which a semiconductor switch and a diode are connected in anti-parallel, 3 is a load, and a snubber circuit 20 is a diode 21, a capacitor 22, a semiconductor switch 23, and two. A so-called ringing choke 2 whose windings are magnetically coupled
It is composed of 4. In reality, the ringing choke 24 requires a reset circuit, but it is not shown here.

The operation of the circuit shown in FIG. 6 will be described with reference to the operation waveform diagram shown in FIG. In FIG. 6, FIG.
As shown in, when the switching circuit 2 is on, the direct current source 1 is short-circuited and no current flows through the load 3. When the switching circuit 2 is off, a current equal to the output current of the direct current source 1 flows through the load 3. The capacitor 22 is for suppressing dv / dt when the semiconductor switch forming the switching circuit 2 is turned off. That is, when the switching circuit 2 is turned off, the direct current source 1
→ diode 21 → capacitor 22 → a current path of the direct current source 1 is formed. At this time, the voltage across the switching circuit 2 (FIG. 7B) is equal to the voltage across the capacitor 22 (FIG. 7C), and this voltage rises more slowly than in the case without the capacitor 22. Switching loss is reduced.

As shown in FIG. 7, in order to continuously perform the above operation, it is necessary to discharge the electric charge accumulated in the capacitor 22 by the next turn-off (see FIG. 7C). Therefore, the electric charge (energy) accumulated in the capacitor 22 is regenerated to the load 3 by the discharge circuit including the semiconductor switch 23, the ringing choke 24, and the diode 25. The semiconductor switch 23 performs an on / off operation at the same timing as the switching circuit 2 (see FIG. 7A).

When the semiconductor switch 23 is turned on, FIG.
A current I ₁ as shown in (d) flows, and the energy of the capacitor 22 is transmitted to the ringing choke 24. When the capacitor voltage (V _C ) becomes 0 (see FIG. 7C), current continues to flow in the path of switching circuit 2 → diode 21 → ringing choke 24 → semiconductor switch 23 → switching circuit 2.

When the semiconductor switch 23 is turned off, FIG.
The current I ₂ as shown in (e) flows and the energy is the load 3.
Is transmitted to FIG. 8: is a circuit block diagram which shows the 2nd prior art example of a power converter device. In FIG. 8, 101 is an alternating current source, 102 is a first main diode, 103 is a second main diode, and 104 to 107 are first to fourth switching circuits in which semiconductor switches and diodes are connected in antiparallel.
8 is a transformer having a center tap, 109 is a load, 110
Is a clamp capacitor.

When the current polarity of the alternating current source 101 is positive, the first main diode 102 becomes conductive. At this time the first
Switching circuit 104 and third switching circuit 106
When both and are turned on, the transformer 108 is connected to the alternating current source 1
01 to the first switching circuit 104-> transformer 108 terminal U-> current flowing in the path of the transformer 108 terminal N and the alternating current source 101 to the third switching circuit 106-> transformer 108 terminal V-> transformer 108 terminal N path Currents flowing in the transformer 10 have the same value, and the respective currents are the same as those in the transformer 10.
Since the magnetic fluxes generated inside 8 cancel each other, transformer 1
No voltage is generated in the secondary winding of No. 08, and no current flows in the load 109.

From the above state, the third switching circuit 1
When 06 is turned off and the first switching circuit 104 is turned on, a positive voltage is applied to the secondary winding of the transformer 108, the first switching circuit 104 is turned off, and the third switching circuit 1
When 06 is turned on, a negative voltage is generated in each of the secondary windings of the transformer 108. That is, the first switching circuit 104 and the third switching circuit 106 are alternately turned off after a period in which both the first switching circuit 104 and the third switching circuit 106 are turned on, whereby a voltage having a frequency higher than the frequency of the alternating current source 101 is supplied to the transformer 1.
08 can be applied.

When the current polarity of the alternating current source 101 is negative, the second main diode 103 becomes conductive, and the second switching circuit 105 and the fourth switching circuit 107 operate in the same manner as described above. In FIG. 8, in order to suppress dv / dt when the first to fourth switching circuits are turned off, there is also a method of providing the snubber circuit 20 shown in FIG. 6 in each of the first to fourth switching circuits. The snubber circuit 200 shown in FIG. 8 can achieve the same effect with a simpler configuration. For example, in the above operation,
When the first switching circuit 104 is turned off, the third switching circuit 106 is on. Therefore, the voltage across the first switching circuit 104 is
Is the same as the voltage between the U and V terminals, and the same applies to other switching circuits.

Therefore, dv / of the voltage between the U and V terminals of the transformer
By suppressing dt, dv / dt of each of the first to fourth switching circuits in the above operation can be suppressed. In the snubber circuit 200, the diodes 201-
A bridge rectifier circuit is composed of 204, and a capacitor 2
05 is connected. When the first switching circuit 104 is turned off, the first switching circuit 104 → transformer 108
The current flowing through the path of the terminal U flows through the path of the third switching circuit 106 → transformer 108 terminal V → diode 202 → capacitor 205 → diode 203 → transformer 108 terminal U, and charges the capacitor 205. At this time, the voltage between the UV terminals of the transformer 108, that is, the voltage across the first switching circuit 104 becomes equal to the voltage across the capacitor 205, and dv / dt is suppressed. The electric charge of the capacitor 205 is discharged by the same method as that of FIG. 6 described above, and the semiconductor switch 207 and the ringing choke 20.
6, through the diode 208, the capacitor 20
The charge of 5 is transferred to the clamp capacitor 110.

The charge of the clamp capacitor 110 is discharged, for example, by turning on the second switching circuit 105 when the first switching circuit 104 is turned off. At this time, the clamp capacitor 110 → the third switching circuit is turned on. 106 → transformer 108 terminal V → transformer 10
A current path of 8 terminals U → second switching circuit 105 → clamp capacitor 110 is formed, and the energy accumulated in the clamp capacitor 110 is transmitted to the load 109 via the transformer 108.

[0014]

In the snubber circuit of the conventional power converter described above, a semiconductor switch for regenerating energy absorbed in the snubber circuit to a power source or a load,
Since a regenerative circuit such as a ringing choke is required, the power conversion device becomes large and expensive, and the reliability is lowered.

An object of the present invention is that a snubber circuit suppresses dv / dt when the power converter operates, and energy absorbed by the snubber circuit can be regenerated to a power source or a load with a simple circuit configuration. To do.

[0016]

According to a first aspect of the present invention, a switching circuit constituted by an antiparallel connection of a semiconductor switching element and a diode is connected between the positive and negative electrodes of a direct current source,
In a power conversion device that controls power to a load connected in parallel to the DC current source by turning on / off the switching circuit, a CDC series circuit in which a first capacitor, a first diode, and a second capacitor are connected in series is provided. It is connected between the positive and negative electrodes of the DC current source, the first reactor and the second diode are connected in series, and is connected between the anode of the first diode and the negative electrode of the DC current source, and the second reactor is connected. A third diode is connected in series and is connected between the cathode of the first diode and the positive electrode of the direct current source.

A second aspect of the present invention is the first invention in which a second switching circuit having the same structure is connected in series to a first switching circuit composed of an antiparallel connection of a semiconductor switch element and a diode.
The switching series circuit and a second switching series circuit in which a third switching circuit and a fourth switching circuit having the same configuration are connected in series are connected in parallel to each other and connected between the positive and negative electrodes of the direct current source, Or a power converter that controls power to a load connected between an intermediate connection point of the first switching series circuit and an intermediate connection point of the second switching series circuit by turning on / off each of the fourth switching circuits. In, a CDC series circuit in which a first capacitor, a first diode, and a second capacitor are connected in series is connected between the positive and negative electrodes of the DC current source, and the first reactor and the second diode are connected in series. One diode is connected between the positive electrode and the negative electrode of the direct current source,
When the reactor and the third diode are connected in series, the first
It is connected between the cathode of the diode and the positive electrode of the direct current source.

Further, a main diode series circuit in which a first main diode and a second main diode are connected in series, a clamp capacitor, and a first switching circuit constituted by an antiparallel connection of a semiconductor switch element and a diode have the same structure. A first switching series circuit in which a second switching circuit is connected in series and a second switching series circuit in which a third switching circuit and a fourth switching circuit of the same configuration are connected in series are connected in parallel to each other, and a transformer having an intermediate tap is provided. Connecting one end of the transformer primary winding to the intermediate connection point of the first switching series circuit, and connecting the other end of the transformer primary winding to the intermediate connection point of the second switching series circuit, the main diode An alternating current source is connected between the intermediate connection point of the series circuit and the intermediate tap of the transformer primary winding,
A power converter for controlling power to a load connected to both ends of the transformer secondary winding by turning on / off each of the fourth switching circuits, the third invention is the first invention.
The first CDC series circuit in which the first capacitor, the eleventh diode, and the twelfth capacitor are connected in series and the second CDC series circuit in which the twenty-first capacitor, the twenty-first diode, and the twenty-second capacitor are connected in series are connected in antiparallel to each other, and A first switching series circuit is connected between an intermediate connection point and the second switching series circuit between intermediate connection points, and an eleventh reactor and a twelfth diode are connected in series to form an anode of the eleventh diode and the second switching circuit. Is connected to the negative power source side of the diode, and a twelfth reactor and a thirteenth diode are connected in series to form a cathode of the eleventh diode and the first diode.
It is connected between the switching circuit and the positive power source side, and the twenty-first reactor and the twenty-second diode are connected in series to each other.
One diode is connected between the anode and the negative power source side of the fourth switching circuit, and the twenty-second reactor and the twenty-third diode are connected in series to form the cathode of the twenty-first diode and the positive power source side of the third switching circuit. And a 15th diode in parallel with the 11th capacitor,
A sixteenth diode is connected in parallel to the twelfth capacitor, a twenty-fifth diode is connected in parallel to the twenty-first capacitor, a twenty-sixth diode is connected in parallel to the twenty-second capacitor, and a fourth invention is an eleventh capacitor and a tenth capacitor. The 11th CDC series circuit in which the 11th diode, the 14th diode, and the 12th capacitor are connected in series, and the 21st CDC series circuit in which the 21st capacitor, 21st diode, 24th diode, and 22nd capacitor are connected in series are connected in antiparallel. And connecting between the intermediate connection point of the first switching series circuit and the intermediate connection point of the second switching series circuit, and connecting the eleventh reactor and the twelfth diode in series to connect the anode of the eleventh diode to the anode. The twelfth reactor and the thirteenth diode are connected between the second switching circuit and the negative power supply side. A column connection is made to connect between the cathode of the 14th diode and the positive power supply side of the first switching circuit, and a 21st reactor and a 22nd diode are connected in series to make an anode of the 21st diode and the 4th diode. The switching circuit is connected to the negative power supply side, the 22nd reactor and the 23rd diode are connected in series, and is connected between the cathode of the 24th diode and the positive power supply side of the third switching circuit. The 15th diode is connected in parallel to the 11th capacitor, the 16th diode is connected in parallel to the 12th capacitor, the 25th diode is connected in parallel to the 21st capacitor, and the 26th diode is connected to the 22nd capacitor.
A diode is connected in parallel, and the eleventh diode and the first diode are connected.
A connection point with four diodes, a connection point between the twenty-first diode and the twenty-fourth diode, and an intermediate tap of the transformer primary winding are connected in parallel with each other.

[0019]

According to the first and second aspects of the present invention, when the respective switching circuits are turned off, the first and second capacitors of the CDC series circuit are charged, respectively, and dv / dt.
Is suppressed. When the switching circuit turns on,
Energy of the first and second capacitors is transmitted to the first and second reactors through a path between the switching circuit, the second diode and the first reactor, and a path between the switching circuit, the third diode and the second reactor. When the respective switching circuits are turned off again, the series circuit of the first reactor and the second reactor formed via the first diode is connected in parallel to the load, and the energy of the first and second reactors is regenerated to the load. It

According to the third and fourth aspects of the invention, when the first switching circuit is turned off, the series circuit of the eleventh capacitor and the twelfth capacitor formed via the eleventh diode is the third switching circuit. Through the first
The eleventh and twelfth capacitors are connected in parallel with the switching circuit and are charged. When the first switching circuit is turned on, both ends of the twelfth capacitor are turned into the twelfth capacitor.
The energy of the twelfth capacitor is transferred to the twelfth reactor via the reactor. When the fourth switching circuit is turned on, both ends of the eleventh capacitor are connected via the eleventh reactor, and the energy of the eleventh capacitor is transferred to the eleventh reactor.

When the first switching circuit is turned off, the twelfth reactor is connected in parallel with the clamp capacitor via the thirteenth diode, the sixteenth diode and the second switching circuit, and the energy of the twelfth reactor is transferred to the clamp capacitor. When the fourth switching circuit is turned off, the eleventh reactor is connected in parallel to the clamp capacitor via the twelfth diode, the fifteenth diode, and the third switching circuit,
Energy of one reactor is transferred to the clamp capacitor.

Similarly, when the second switching circuit is turned off, the 21st and 22nd capacitors are charged respectively, and the energy thereof is passed through the 21st and 22nd reactors according to the turning on / off of the 2nd and 3rd switching circuits, respectively. Transmitted to the clamp capacitor. Also, the third
When the switching circuit is turned off, the 21st and 22nd
The capacitors are respectively charged, and the energy thereof is transmitted to the clamp capacitors via the 21st and 22nd reactors, respectively, as the second and third switching circuits are turned on / off.

When the fourth switching circuit is turned off, the eleventh and twelfth capacitors are charged respectively, and the energy of the capacitors is charged through the eleventh and twelfth reactors according to the on / off of the first and fourth switching circuits, respectively. Be transmitted to. The energy transferred to the clamp capacitor is regenerated to the load by the operation of the switching circuit similar to that of the second conventional example described above.

[0024]

In the following embodiments of the present invention, members having the same functions as those of the conventional example shown in FIGS. 6 and 8 are designated by the same reference numerals and the description thereof will be omitted. explain. 1 is a circuit configuration diagram of a power converter according to a first embodiment of the present invention.

In FIG. 1, a switching circuit 2 and a load 3 are connected in parallel with a direct current source 1, and a snubber circuit 10 is a CDC series circuit composed of a first capacitor 14, a first diode 12 and a second capacitor 15. It is connected in parallel to the circuit 2, and a series circuit composed of the first reactor 16 and the second diode 11 is connected between the anode of the first diode 12 and the negative power supply side of the switching circuit 2, and the cathode of the first diode 12 is also connected. And the positive power supply side of the switching circuit 2 between the second reactor 17 and the third diode 13
Connect a series circuit consisting of.

The operation of the power converter of FIG. 1 will be described with reference to the operation waveform diagram of the power converter of FIG. 1 shown in FIG. In FIG. 1, when the switching circuit 2 is turned off (see FIG. 2A), the voltage V of the first capacitor 14 is
c ₁ (FIG. 2C), the voltage Vc _{2 of} the second capacitor 15
(FIG. 2C) is charged at a slow voltage increase rate, so that the switching loss of the switching circuit 2 is reduced. When the switching circuit 2 is turned on (Fig. 2
(See (a)), the energy of the first and second capacitors is
It is transmitted to the first and second reactors through the path of the switching circuit 2 → the second diode 11 → the first reactor 16 and the path of the switching circuit 2 → the third diode 13 → the second reactor 17 (FIG. 2D). reference). When the switching circuit 2 is turned off again, the series circuit of the first reactor and the second reactor formed via the first diode 12 is connected in parallel to the load, and the energy of the first and second reactors is regenerated to the load. (See FIG. 2D).

FIG. 3 is a circuit configuration diagram of a power converter showing a second embodiment of the present invention. The power converter of FIG. 3 is called a current source inverter, and includes a series circuit of the first switching circuit 4 and the second switching circuit 5, and a series circuit of the third switching circuit 6 and the fourth switching circuit 7. Each is connected in parallel to the direct current source 1.
In addition, the first switching circuit 4 and the second switching circuit 5
The load 3 is connected between the connection point of and the connection point of the third switching circuit 6 and the fourth switching circuit 7. The snubber circuit 10 has the same configuration as the snubber circuit 10 of FIG.

The operation of the circuit shown in FIG. 3 will be described below. First
~ When the fourth switching circuit is turned on, the direct current source 1
Is short-circuited and no current flows through the load 3 (so-called short-circuit period). 1st, 4th switching circuit is ON, 2nd, 3rd
The switching circuit is off and a positive current flows through the load 3 (so-called positive current period), the second and third switching circuits are on, the first and fourth switching circuits are off, and a negative current flows through the load (so-called negative current). Current period). The positive current period and the negative current period are alternately repeated with a short circuit period interposed therebetween, thereby converting a direct current into an alternating current. The voltage waveform between P and M shown in FIG. 3 during this operation is exactly the same as the voltage waveform across the switching circuit shown in FIG. 2B, and the applied voltage at the turn-off of the first to fourth switching circuits. Is equal to the voltage between P and M shown in FIG. Therefore, the operation and the effect of the snubber circuit 10 are the same as those of the snubber circuit of FIG.

FIG. 4 is a circuit configuration diagram of a power converter showing a third embodiment of the present invention. In FIG. 4, first to
The power conversion operation by the fourth switching circuit is the same as that of the second conventional example shown in FIG.
The snubber circuit 300 will be described below. That is, in FIG. 4, the first capacitor 313, the eleventh diode 305, and the twelfth capacitor 314 are used as the first capacitor.
CDC series circuit, 21st capacitor 312, 21st capacitor
The diode 302 and the second CDC series circuit including the 22nd capacitor 311 are connected to the first switching circuit 104.
And a connection point between the second switching circuit 105 and the connection point between the third switching circuit 106 and the fourth switching circuit 107 are connected in anti-parallel as illustrated.

A series circuit including a twelfth reactor 316 and a thirteenth diode 308 is connected between the cathode of the eleventh diode 305 and the positive power source side of the first switching circuit 104. The anode of the eleventh diode 305 and the second
A series circuit including the eleventh reactor 317 and the twelfth diode 309 is connected between the switching circuit 105 and the negative power supply side.

A series circuit including a twenty-second reactor 315 and a twenty-third diode 307 is connected between the cathode of the twenty-first diode 302 and the positive power source side of the first switching circuit 104. The anode of the twenty-first diode 302 and the second
A series circuit including a 21st reactor 318 and a 22nd diode 310 is connected between the switching circuit 105 and the negative power supply side.

The 26th diode 30 is connected in parallel with the 22nd capacitor 311, the 21st capacitor 312, the 11th capacitor 313, and the 12th capacitor 314, respectively.
1, 25th diode 303, 15th diode 30
The fourth and fifteenth diodes 306 are connected in the direction shown in FIG. The operation of the snubber circuit 300 has been described in detail in the above-mentioned “Operation” section, and thus the description thereof is omitted here.

FIG. 5 is a circuit configuration diagram of a power converter showing a fourth embodiment of the present invention. The snubber circuit 400 of the power converter shown in FIG. 5 and the snubber circuit 3 shown in FIG.
The operation is the same as that of 00, but the difference is that the twenty-first diode 302 and the eleventh diode 305 of FIG. The connection point between the 302 and the 24th diode 402, and the 11th
This is the point where the connection point between the diode 305 and the fourteenth diode 401 and the N terminal of the transformer 108 are connected in parallel with each other.

As a result, for example, when the first switching circuit 104 is turned off and the 22nd reactor 315 releases energy, the 22nd reactor 315 → the 2nd reactor 315
The path formed by the third diode 308 → the third switching circuit 106 → the transformer 108 terminal V → the transformer 108 terminal N → the 24th diode 402 → the 22nd reactor 315 is formed, and the energy is directly transformed without passing through the clamp capacitor 110. It is transmitted to the load 109 on the secondary side of 108. Therefore, the loss during energy regeneration is suppressed to be smaller than that of the snubber circuit 300 of FIG.

[0035]

According to the present invention, the energy of the capacitor of the CDC series circuit is transmitted to the reactor when the switching circuit is turned on, and the energy of the reactor is transmitted to the load when the switching circuit is turned off again. In this way, energy can be regenerated only by turning the switching circuit on and off, the snubber circuit configuration is simple, the size and cost are low, and the semiconductor switch circuit for energy regeneration is not required. Is improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a power conversion device showing a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram for explaining the operation of FIG.

FIG. 3 is a circuit configuration diagram of a power conversion device showing a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a power conversion device showing a third embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of a power conversion device showing a fourth embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of a power conversion device showing a first conventional example.

7 is an operation waveform chart for explaining the operation of FIG.

FIG. 8 is a circuit configuration diagram of a power conversion device showing a second conventional example.

[Explanation of symbols]

1 ... DC current source, 2 ... switching circuit, 3 ... load, 4
~ 7 ... switching circuit, 10 ... snubber circuit, 11 to 1
3 ... Diode, 14, 15 ... Capacitor, 16, 17
… Reactor, 20… Snubber circuit, 21… Diode,
22 ... Capacitor, 23 ... Semiconductor switch, 24 ... Ringing choke, 25 ... Diode, 101 ... AC current source, 102-103 ... Diode, 104-107 ... Switching circuit, 108 ... Transformer, 109 ... Load, 11
0 ... Clamp capacitor, 200 ... Snubber circuit, 201
~ 204 ... Diode, 205 ... Capacitor, 206 ...
Ringing choke, 207 ... Semiconductor switch, 208
... Diode, 300 ... Snubber circuit, 301-310 ...
Diodes, 311 to 314 ... Capacitors, 315 to 3
18 reactors, 400 ... Snubber circuits, 401, 402
…diode.

Claims (4)

[Claims] 1. A switching circuit composed of an anti-parallel connection of a semiconductor switch element and a diode, comprising a positive current source,
In a power conversion device connected between negative electrodes and controlling power to a load connected in parallel to the DC current source by ON / OFF operation of the switching circuit, a first capacitor, a first diode, and a second capacitor are connected in series. The connected CDC series circuit is connected between the positive and negative electrodes of the DC current source, and the first reactor and the second diode are connected in series to connect between the anode of the first diode and the negative electrode of the DC current source. The second reactor and the third diode are connected in series and are connected between the cathode of the first diode and the positive electrode of the direct current source, and the snubber circuit of the power converter. 2. A first switching series circuit in which a second switching circuit having the same configuration is connected in series to a first switching circuit configured by an anti-parallel connection of a semiconductor switch element and a diode, a third switching circuit having the same configuration, and a third switching circuit having the same configuration. A second switching series circuit in which four switching circuits are connected in series are connected in parallel to each other and connected between the positive and negative electrodes of the direct current source, and each of the first to fourth switching circuits is turned on.
In a power converter that controls power to a load connected between an intermediate connection point of the first switching series circuit and an intermediate connection point of the second switching series circuit by an off operation, a first capacitor and a first diode And a second capacitor are connected in series to connect a CDC series circuit between the positive and negative electrodes of the DC current source, and the first reactor and the second diode are connected in series to form the anode of the first diode and the DC current source. A second reactor and a third diode are connected in series and are connected between the cathode of the first diode and the positive electrode of the direct current source. Snubber circuit. 3. A main diode series circuit in which a first main diode and a second main diode are connected in series, a clamp capacitor, and a first switching circuit having the same configuration as an anti-parallel connection of a semiconductor switch element and a diode. A first switching series circuit in which a second switching circuit is connected in series and a second switching series circuit in which a third switching circuit and a fourth switching circuit of the same configuration are connected in series are connected in parallel to each other, and a transformer having an intermediate tap is provided. Connecting one end of the transformer primary winding to the intermediate connection point of the first switching series circuit, and connecting the other end of the transformer primary winding to the intermediate connection point of the second switching series circuit, the main diode An alternating current source is connected between an intermediate connection point of a series circuit and an intermediate tap of the transformer primary winding, and the first to fourth switching elements are connected. Turn on each circuit
In a power converter that controls power to a load connected to both ends of the transformer secondary winding in an off operation, a first CDC series circuit in which an eleventh capacitor, an eleventh diode, and a twelfth capacitor are connected in series, Between the intermediate connection point of the first switching series circuit and the intermediate connection point of the second switching series circuit by connecting the 21st capacitor, the 21st diode, and the second CDC series circuit in which the 22nd capacitor is connected in series in anti-parallel. And an eleventh reactor and a twelfth diode are connected in series to connect between the anode of the eleventh diode and the negative power source side of the second switching circuit, and the twelfth reactor and the thirteenth diode are connected in series. Connected between the cathode of the eleventh diode and the positive power supply side of the first switching circuit to connect the twenty-first reactor and the twenty-second die. Connected in series between the anode of the twenty-first diode and the negative power source side of the fourth switching circuit, and the twenty-second reactor and the twenty-third diode in series to form the cathode of the twenty-first diode. It is connected between the third switching circuit and the positive power source side, the 15th diode is connected in parallel to the 11th capacitor, the 16th diode is connected in parallel to the 12th capacitor, and the 25th diode is connected to the 21st capacitor. Are connected in parallel, and the 26th diode is connected in parallel to the 22nd capacitor. A snubber circuit of a power conversion device. 4. A main diode series circuit having a first main diode and a second main diode connected in series, a clamp capacitor, and a first switching circuit having the same configuration as an anti-parallel connection of a semiconductor switch element and a diode. A first switching series circuit in which a second switching circuit is connected in series and a second switching series circuit in which a third switching circuit and a fourth switching circuit of the same configuration are connected in series are connected in parallel to each other, and a transformer having an intermediate tap is provided. Connecting one end of the transformer primary winding to the intermediate connection point of the first switching series circuit, and connecting the other end of the transformer primary winding to the intermediate connection point of the second switching series circuit, the main diode An alternating current source is connected between an intermediate connection point of a series circuit and an intermediate tap of the transformer primary winding, and the first to fourth switching elements are connected. Turn on each circuit
A power conversion device for controlling power to a load connected to both ends of the transformer secondary winding in an off operation, wherein an eleventh capacitor, an eleventh diode, a fourteenth diode, and a twelfth capacitor are connected in series. Series circuit, 21st capacitor, 21st diode, 2nd
Second with 4 diodes and 22nd capacitor connected in series
1CDC series circuit is connected in anti-parallel and connected between the intermediate connection point of the first switching series circuit and the intermediate connection point of the second switching series circuit, and the eleventh reactor and the twelfth diode are connected in series. It is connected between the anode of the eleventh diode and the negative power source side of the second switching circuit, the twelfth reactor and the thirteenth diode are connected in series, and the cathode of the fourteenth diode and the positive electrode of the first switching circuit are connected. It is connected between the power supply side and the twenty-first reactor and the twenty-second diode are connected in series to be connected between the anode of the twenty-first diode and the negative power supply side of the fourth switching circuit. 23 diodes are connected in series and connected between the cathode of the 24th diode and the positive power supply side of the third switching circuit, and the 11th capacitor A 15th diode is connected in parallel, a 16th diode is connected in parallel to the 12th capacitor, a 25th diode is connected in parallel to the 21st capacitor, a 26th diode is connected in parallel to the 22nd capacitor, and A connection point between the diode and the fourteenth diode, a connection point between the twenty-first diode and the twenty-fourth diode, and an intermediate tap of the transformer primary winding are connected in parallel with each other. Snubber circuit.